Amazon spent years developing the checkout-less technology behind the store, and another year testing it with Amazon employees before the original store opened in January in the base of Amazon’s Day One officer tower. But since then, Amazon has embarked on an expansion of the concept.

New York represents the third market outside of Seattle where Amazon plans to open Amazon Go stores. In May, the company confirmed plans to open stores in San Francisco and Chicago.

The store relies heavily on the Amazon Go smartphone app. Customers scan a unique QR code within the app before passing through a set of glass doors, similar to the gates Amazon employees go through when entering their office buildings every morning. A vast array of overhead cameras and weight sensors in the shelves automatically track what people pick up and take from the store.

When customers leave, they just walk out. Amazon Go’s systems automatically debit their accounts for the items they take, sending the receipt to the app. By logging shoppers in at the entrance, then tracking their actions in the store, the system eliminates the need for traditional checkout registers and checkout workers along with them.

Nat Levy is a staff reporter at Geekwire covering a variety of technology topics, including Microsoft, Amazon, tech startups, and the intersection of technology with real estate, courts and government. Contact him at nat@geekwire.com and follow him on Twitter at @natjlevy.